1. Field of the Invention
The present invention concerns a gas barrier film and, more specifically, it relates to a laminate type gas barrier film suitable to substrates for various kinds of devices and coating films for the devices. Further, the invention also relates to an organic electroluminescence device excellent in durability and flexibility obtained by using the gas barrier film (referred to hereinafter as an organic EL device).
2. Description of the Related Art
Gas barrier films in which thin films of metal oxide such as aluminum oxide, magnesium oxide, and silicon oxide are formed on the surfaces of plastic substrates or films have been generally used so far for packaging of articles requiring shielding of steams or various gases such as oxygen, or packaging application for preventing denaturation of foodstuffs, industrial products, and medicines. Further, the gas barrier films have also been started for use in substrates of liquid crystal display devices, solar cells or EL devices in addition to the packaging use. Particularly, in transparent substrates which have been applied progressively to liquid crystal display devices, EL devices, etc., high level of demands such as long time reliability, high degree of freedom in view of shape, and capability of display on a curved surface have been required in addition to the demand for reduction in the weight and increase in the size.
In recent years, in the field of the liquid crystal display devices, the EL devices, etc., film substrates such as made of transparent plastics have been started for use instead of glass substrates, which are heavy, tended to be cracked and difficult in increasing the area. Further, since the plastic substrates such as made of transparent plastics not only can cope with the requirements described above but also can be applied to the roll-to-roll system, they are advantageous over glass materials in view of the productivity and the reduction of cost. However, film substrates of transparent plastics involve a problem of poor gas barrier property in comparison with glass substrate. In a case of using a substrate of poor gas barrier property, since steam or air permeates when it is used, for example, to a liquid crystal display device, liquid crystals in a liquid crystal cell are deteriorated and deteriorated portions result in display defects to worsen the display quality.
For solving such problems, it has been known to form a thin film of a metal oxide on the film substrate described above, and use the gas barrier film as a transparent substrate. As gas barrier films used for packaging materials and liquid crystal display devices, those formed by vapor depositing silicon oxide on a plastic film (for example, refer to JP-B No. 53-12953 (p1 to p3)) and those formed by vapor depositing aluminum oxide (for example, refer to JP-A No. 58-217344 (p1 to p4)) are known and both of them have a steam barrier property of about 1 g/m2/day. However, the steam barrier property as low as about 0.1 g/m2/day has been demanded recently for the film substrate along with increase in the size of liquid crystal displays or development for highly fine displays.
Further, most recently, development has been progressed, for example, in organic EL displays or highly fine color liquid crystal displays requiring further higher barrier property and it has been demanded for a substrate having a performance of higher barrier property, particularly, a steam barrier property of less than 0.1 g/m2/day while maintaining transparency usable therein.
For coping with such a demand, film formation by way of a sputtering method or a CVD method of forming a thin film using plasmas generated by glow discharge under low pressure conditions has been studied as means capable of expecting higher barrier performance. Further, it has been attempted to obtain desired performance by a lamination structure (for example, refer to JP-A No. 2003-206361 (p2 to p3).
However, in a case of using the film substrate, since restriction is imposed on the substrate temperature during film formation, a barrier layer of a sufficiently dense structure can not be formed, and a film having a barrier property enough to satisfy the requirement has not yet been manufactured.
As a thin film material of excellent barrier property, silicon nitride and silicon oxynitride are also utilized and it has been attempted to laminate them (refer, for example, to JP-A No. 2003-206361 (P2 to P3)).
However, a constitution capable of compatibilizing a sufficient barrier property and bending resistance required in the use of the substrate film has not yet been reached, and a further technical development has been demanded.
On the other hand, it has been proposed a technique of preparing a barrier film having an alternate laminate structure of organic layer/inorganic layer by a vapor deposition method (for example, refer to U.S. Pat. No. 6,413,645B1 (p4, [2-54] to p8, [8-22])) and “Thin Solid films” written by Affinito, et al., (1996), p. 290 to p291 (p63 to p67)), and a film having a barrier property necessary for the film substrate for organic EL device is obtained.
However, in a case of continuously forming the films for the organic layer and the inorganic layer, it gives rise to a problem such as contamination between both of the processes, and it is necessary to form a multi-layered structure by six or more layers in order to provide a barrier film of high reliability for use in organic EL devices. Since it has been difficult to make the performance and the high throughput compatible, it has been demanded for developing a new film forming system suitable to continuous film forming process.